Medizinische Universität Graz Austria/Österreich - Forschungsportal - Medical University of Graz
Gewählte Publikation:
Hofer, D.
Vitamin D and testosterone- is there a relationship?
PhD-Studium (Doctor of Philosophy); Humanmedizin; [ Dissertation ] Medical University of Graz; 2014. pp. 123
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- Autor*innen der Med Uni Graz:
- Sudy Daniela
- Betreuer*innen:
- Fröhlich Eleonore
- Obermayer-Pietsch Barbara
- Rinner Beate
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- Abstract:
- Background: Vitamin D is well known for its function in calcium and bone homeostasis. We have already published based on clinical data that vitamin D and testosterone serum levels in men are saisonal associated. In addition, signalling through the vitamin D receptor (VDR) seems to be of high importance for testicular function, such as spermatogenesis and the synthesis of androgens in rodent models. The bone derived hormone osteocalcin (OC) has been shown to influence male testosterone production by inducing the transcription and synthesis of androgenic genes. Methods: We have performed pre-experiments using animal testis tissue and established a protocol for the isolation of testicular cells. Human testicular primary cells were isolated from human testis tissue, which was derived either from organ donors at the Division of Transplantation Surgery, or from semi-orchidectomized patients due to small testicular cancer at the Department of Urology, in both cases healthy testis explants. Cells were cultured for several weeks to test various stimuli and dosages of vitamin D effects. The testicular carcinoma cell line Ntera2/d1 (NT2/d1) was used to test cell viability. RNA microarrays were performed to screen for vitamin D effects in human testicular cells on transcript level. Effects of 1,25(OH)2D, luteinizing hormone (LH), insulin-like growth factor 1 (IGF-1), OC, as well as testosterone on gene expression of selected genes of the androgen and vitamin D synthesis pathway, respectively, were analyzed using real time quantitative PCR (RT-qPCR). Testosterone and dihydrotestosterone in the cell culture supernatants were analyzed using testosterone enzyme-linked immunosorbent assays (ELISAs). The expression of VDR in human testicular cells was shown by immunocytochemistry. Results: In pre-studies using porcine testicular cells, we have shown a dose-dependent effect of 25(OH)D and 1,25(OH)2D on mRNA level of selected genes. Our studies in human testicular cell cultures have shown that supraphysiological doses of 1,25(OH)2D (100 nM) led to significant alterations in gene expression of reproductive genes. Microarray analysis revealed sixty three genes in testicular cells to be differentially expressed after 1,25(OH)2D treatment, resulting in 56 upregulated and 7 downregulated mRNA transcripts. Supraphysiologic doses of 1,25(OH)2D significantly increased cell proliferation and viability and testosterone concentrations in human testicular cells as measured by WST-1 cell proliferation assay and ELISA, respectively. In testicular carcinoma cells NT2/d1, cell proliferation was not affected by vitamin D. Physiologic doses of osteocalcin increased testosterone and dihydrotestosterone concentrations dose-dependently in testicular primary cells as well as mRNA levels of genes related to the androgen synthesis and metabolism pathway, compared to stimulation with several concentrations of LH. Conclusions: Vitamin D might play a direct role in male steroidogenesis in vitro, probably by the activation of VDR and the induction of vitamin D response elements (VDREs) in the promotor region of target genes that might increase gene expression of genes involved in male androgen synthesis and testosterone production. We could further show activation of gene expression and testosterone production by OC, assuming that vitamin D might act indirectly through bone to induce male steroidogenesis. Signal transduction pathways of vitamin D as well as osteocalcin need to be further claryfied, VitD and OC might be considered as important biomarkers in male fertility.